Question 1

Which of the following statements best explains why autosomal dominant disorders, such as Huntington's disease, can persist in a population even though they are often fatal?

Accepted Answer

The symptoms of autosomal dominant disorders often appear after reproductive age, allowing affected individuals to pass on the allele before knowing they have the disorder.

Question 2

A couple, both of whom are carriers for an autosomal recessive disorder, are planning to have children. What is the probability that their child will be affected by the disorder? Use a Punnett square to justify your answer.

Accepted Answer

$$\frac{1}{4}$$

Question 3

Which of the following best describes the inheritance pattern of cystic fibrosis in humans?

Accepted Answer

Autosomal recessive

Question 4

A woman with type AB blood and a man with type O blood have a child. What are the possible blood types of their child?

Accepted Answer

Type A or Type B

Question 5

Which of the following is an example of codominance in humans?

Accepted Answer

AB blood type, where both A and B antigens are expressed on red blood cells

Question 6

A pedigree shows a trait that appears in every generation and affects males and females equally. Which inheritance pattern is most likely?

Accepted Answer

Autosomal dominant

Question 7

Which of the following best explains why X-linked recessive disorders, such as colorblindness, are more common in males than in females?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will result in the disorder.

Question 8

A man with hemophilia (an X-linked recessive disorder) and a woman who is a carrier have children. What is the probability that their son will have hemophilia?

Accepted Answer

$$\frac{1}{2}$$

Question 9

Which of the following is an example of pleiotropy?

Accepted Answer

Marfan syndrome, where a single gene mutation affects the skeleton, eyes, and cardiovascular system

Question 10

A child is born with a rare autosomal recessive disorder. Neither parent shows symptoms of the disorder. Which of the following best explains this outcome?

Accepted Answer

Both parents are heterozygous carriers of the recessive allele.

Question 11

Which of the following best describes polygenic inheritance?

Accepted Answer

A trait is controlled by two or more sets of alleles, each with an additive effect on the phenotype.

Question 12

In a population, the continuous variation in human skin color is best explained by which genetic principle?

Accepted Answer

Polygenic inheritance

Question 13

Which of the following scenarios is an example of incomplete dominance?

Accepted Answer

A cross between red-flowered and white-flowered plants produces offspring with pink flowers.

Question 14

A woman who is a carrier for colorblindness (an X-linked recessive trait) has children with a man who is not colorblind. What is the probability that their daughter will be colorblind?

Accepted Answer

$$\frac{1}{4}$$

Question 15

Which of the following best describes the concept of multiple alleles?

Accepted Answer

A gene exists in several different allelic forms within a population, but each individual only has two alleles.

Question 16

Which of the following is a real-world example of how environmental factors can influence the expression of a polygenic trait?

Accepted Answer

Children in post-World War II Europe experienced stunted height due to malnutrition, despite their genetic potential for tall stature.

Question 17

If a woman with polydactyly (an autosomal dominant trait with incomplete penetrance) has a child with a man who does not have polydactyly, what is the best explanation if their child does not have extra fingers or toes?

Accepted Answer

The child inherited the dominant allele, but the trait was not expressed due to incomplete penetrance.

Question 18

Which of the following statements about X-linked inheritance is correct?

Accepted Answer

A female can be a carrier for an X-linked recessive disorder without showing symptoms.

Question 19

A pedigree shows that a trait is present in males much more frequently than in females, and affected males often have unaffected parents. Which inheritance pattern does this suggest?

Accepted Answer

X-linked recessive

Question 20

Which of the following best explains why type O blood is considered the universal donor?

Accepted Answer

Type O blood lacks A and B antigens, so it is not recognized as foreign by any recipient's immune system.

Beyond Mendelian Inheritance: Human Genetic Disorders and Complex Patterns

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